[Study of molecular mechanism and antigen expression of CisAB01 blood group]

To explore the molecular mechanism of CisAB01 subtype in the ABO blood group system, and to investigate the expression of A and B antigens in red blood cells (RBCs).

For 5 unrelated individuals with the CisAB phenotype, the molecular basis for the blood type was studied with serological assay, DNA sequencing and haplotype analysis. Bioinformatics analysis was carried out to investigate the changes in structure and function of relevant enzymes. Expression of A and B antigens in RBCs of CisAB01 was detected by flow cytometry.

All of the 5 samples were found to have a CisAB01 subtype. The underlying mutations, 467C>T and 803G>C in exon 7, have resulted in replacement of amino acid P156L and G268A. The mean fluorescence intensity (MFI) of A antigen in CisAB01 cases was 135, while the control group was 172. The B antigens in CisAB01 cases (MFI=38) showed significant decrease in MFI compared with the control group (MFI=164).

803G>C mutation of the ABO gene probably underlies the CisAB01 subtype. Fluorescence intensity of A antigens in CisAB01 subtype cases is slightly lower than the normal type, while the B antigen was significantly lower.